Deck tilt corrector



Jan. 10, 1961 w. H. NEwELL DECK TILT coRREcToR 4 Sheets-Sheet 1 FiledFeb. 18. 1953 von TQ Jan. 10, 1961 w. H. Nx-:wELL

DECK TILT CORRECTOR 4 Sheets-Sheet 2 Filed Feb. 18. 1955 IIIII Il.IIIIII lll lllllllnlllll'll..

Mr y A 06k unNwQQ Jan. 10, 1961 w. H. NEWELL DECK TILT coRREcToR 4Sheets-Sheet 5 Filed Feb. 18. 1953 (Ittorneg 4 Sheets-Sheet 4 W.H..NEWELL DECK TILT CORRECTOR Jan. 10, 1961 Filed Feb. 18. 1953 UnitedStates Patent O DECK TILT CORRECTOR William H. Newell, Mount Vernon,N.Y., assgnor to Sperry Rand Corporation, a corporation of DelawareFiled Feb. 1s, 1953, ser. No. 337,465

1 claim. (C1. zas-61.5)

The invention relates to a method and apparatus for determining the tiltcorrection of an angularly movable control supporting platform or decksuch as that of a ship, and although the invention has a wide range ofutility, it is particularly n'seful in connection with the control ofordnance for anti-aircraft and surface tiring.

The invention has utility, for example, in connection with a re controlsystem, by which guns or like ordnance are controlled from a directorwhich measures the present position of the target in train andelevation, and by which from this data and other data, the predictedposition of the target in train and elevation at the end of the time oftlight of the projectiles is computed. On a ship, director train (i.e.the angle between the vertical plane through the ships centerline andthe vertical plane through the line of observation or sight) is measuredclockwise from the bow in the deck plane. Since the ship will roll andpitch, angles measured in the deck plane usually vary in phase with theships movement and hence must be corrected to determine deflection ratesor other necessary re control quantities.

The mechanization of deck tilt correctional equations derived byempirical means introduces errors affecting the accuracy ofdetermination of deck tilt correction.

One object of the present invention is to provide a new and improvedmethod and instrument by which the values of deck tilt correction (i.e.correction due to inclination from horizontal of a movable deck orplatform supporting at least part of a control, computing or predictingsystem, such as the director of a re cntrol system) are accurately,quickly and continuously computed, thus eliminating the effect ofangular movement of the deck and causing thereby the system to operateas if said part were mounted upon a stable platform.

From the director, there is obtained kthe director train (describedabove) and from a stable element, there is obtained the level angle andthe cross-level angle. The level angle is the angle between the deckplane and the horizontal plane, measured in the vertical plane throughthe line of sight, this angle being considered positive when the portionof the deck towards the target is down, and cross-level angle is theangle between the vertical plane through the line of sight and the planeperpendicular to the deck plane through the intersection of the deckplane and the vertical plane through the line of sight.

As a feature of the present invention, from the level angle, cross-levelangle and director train, a true solution formula is derived for thedeck tilt correction, which is solved continuously for the value of decktilt correction by a servo or null seeking system, which so drives thedeck tilt correction line that a balance is obtained between thequantities on opposite sides of the equality sign of the formula.

Various other objects, features and advantages of the invention areapparent from the following particular description and from inspectionof the accompanying drawings. in which:

ice

Fig. 1 is a simplified block diagram showing the functional connectionsbetween the general computer assembly, of which the deck tilt correctorembodying the present invention may be made a part, and the othercomponents of a gun fire control system;

Fig. 2 is a simplified block diagram showing the parts of a presentposition network directly related to the deck tilt corrector where saidcorrector is employed as part of a gun lire control system;

Fig. 3 is a spherical diagram of the deck tilt problem solved by thepresent invention;

Fig. 4 is a simplied block diagram of the deck tilt corrector embodyingthe present invention; and

Fig. 5 is a simplified basic circuit diagram of a specific example of adeck tilt corrector embodying the present invention.

GLOSSARY A tabulation of symbols and terms used in the drawings and inthe description in connection with a ship and a gun tire control systemthereon is submitted herein.

(B) true target bearing. The angle between true north and the verticalplane through the line of sight, measured in a horizontal planeclockwise from true north (Br) relative target bearing. The anglebetween the vertical plane through the ships centerline and the verticalplane through the line of sight, measured in the horizontal planeclockwise from the bow.

(Br) director train. The angle between the vertical plane through theships centerline and the vertical plane through the line of sight,measured in the deck plane clockwise from the bow.

(jBr) deck tilt correction. Inclination of director roller path fromhorizontal. This correction added t0 director train (Br) results inrelative target bearing (Br) as follows (Co) ship course. The compassheading of the ship.

(E) position angle. The angle between the line of sight and thehorizontal plane, measured in a vertical plane (Eb) director elevation.The angle between the line of sight and the deck plane, measured in thevertical plane through the line of sight, this angle being consideredpositive when the line of sight is elevated.

(L) level angle. The angle between the deck plane and the horizontalplane, measured in the vertical plane through the line of sight, thisangle being considered positive when the portion of the deck toward thetarget is down.

- (R) present range. The distance in yards from the gun director to thetarget.

(Zd) Cross-level angle. The angle between the vertical plane through theline of sight and the plane perpendicular to the deck plane through theintersection of the deck plane and the vertical plane through the lineof sight.

FIRE CONTROL SYSTEM A suitable lire control system in which the decktilt corrector of the present invention -may be employed includes acomputer assembly capable of solving gun tire control problems bothanti-aircraft and surface. Fig. l illustrates in a simplified manner,the connections between such a computer assembly designated by numeral10 and the other components of thesystem including a gun director 11 anda stable element 12. The computer assembly 10 is of so-called linearrates type and includes a present position, rates and accelerationportion for converting target data to a stable reference frame and forcomputing the rates of ship, wind, and target motion and targetacceleration. This portion of the computer assembly is employed duringthe acquisition, tracking and ring phases of each engagement.

The present position network converts the polar coordinates (Br, Eb andR) of relative target position as supplied by the gun director 11 into astable system of polar coordinates (B, E and R) whose values do notchange with the rolling, pitching and changes in course of own ship. Thelevel angle (L) and cross-level angle (Zd) supplied by the stableelement 12 are used to refer the director outputs to a horizontal plane,while own ship course from the re control gyro compass 16, is used toestablish a north-south reference.

Fig. 2 shows a diagram of part of the present position network 13 andespecially that part around the deck tilt corrector 14, which will bedescribed hereinafter. In this present position network, the directortrain (Br) measured in the tiltable deck plane and derived from the gundirector 11 (Fig. 1) and the level angle (L) and the crosslevel angle(Zd) derived from the stable element 12 (Fig. 1), are put into the decktilt corrector (Fig. 2) to obtain the deck tilt correction (J'Br). Thisdeck tilt correction (jBr) and the director train (Br) are added in acomponent such as a differential 15 to obtain the relative targetbearing (Br) according to the equation Br=B'r+jBr Ship course (Co) fromthe fire control gyro compass 16 (Fig. 1), is combined with relativetarget bearing (Br) in an adding component such as the dilerential 17 toform the true target bearing (B) as follows:

This true target bearing (B) is sent to the linear rates network (notshown) and especially to the apparent wind network, which forms part ofthe computer assembly (Fig. 1) and which performstwo functions; itsupplies the range and deection components of apparent wind to theballistic network (not shown) and it supplies the components of own shipvelocity to the linear rates network (not shown). The ballistic networkcomputes all the corrections that the curved nature of the trajectory ofthe projectile requires, and the linear rates network takes inputs fromthe present position, apparent wind and ballistic networks, and fromthese inputs computes the deection, horizontal range and height ratesand accelerations.

The ship course (Co) also drives one of the generators 18 (Fig. 2) whoseoutput d(Co) is used at the gun director 11 (Fig. 1) as an aid intracking.

Aside from the present position problem, the correction (jBr) from thedeck tilt corrector 14 (Fig. 2) also drives another generator 18, whoseoutput is the rate of change of (J'B'r) or d(]'B'r). This quantity issent to the gun director 11 (Fig. 1) to aid in the tracking problem.

Derivation of true solution formula for deck tilt correction jBr Inaccordance with the present invention, a true solution for the deck tiltproblem is employed, thereby eliminating errors, such as those thatwould be inherent if empirical solution were employed. As a result ofthe procedure of the present invention, a true solution formula isobtained containing as terms the deck tilt correction (J'Br), the levelangle (L), the cross-level angle (Zd), the relative target bearing (Br)and the director train (Br). This formula is solved for the deck tiltcorrection (jBr) by a servo or null seeking system, which so drives the(JB'r) line that a balance is obtained between the quantities onopposite sides of the equation.

The deck tilt problem is indicated in the spherical diagram shown inFig. 3. This problem is solved in accord- '4 ance with a true solution,using as inputs the level angle (L) and the cross-level angle (Zd)obtained from the stable element 12 (Fig. 1) on the ship or craftcarrying the re control system, and the director train (Br) in` deckplane obtained from the gun director 11, to derive the relative targetbearing or director train (Br) in horizontal plane.

Applying the rules of spherical trigonometry to the triangle formed by(H), (0) and (9D-L) (Fig. 3), the following expressions may be written(1) sin (H )=sin (Br) sin (9D-L) sin (H) =sin (Br) cos (L) (2) cos (Br):sin (0) cos (H) (3) cot (Br) cot (0)=cos (90-L) cot (H)=sin (L) tan(Br) (4) sin (0) cos (H) substituting the following in Expression 4 sin(Zd) cot (0H-cos (Zd)= (a) sin (Br) cos (L) for sin (H) from (1) (b) cos(Br) for sin (6) cos (H) from (2) (c) sin (L) tan (Br) for cot (0) from(3) there is obtained sin (Zd) sin (L) tan (BTH-cos (Zd)= Y cot (Br) sin(Br) cos (L) cos (Br) sin (zd) sin (L) tan (BTHGOS (zdF-(cg-@Multiplying by cot (Br), there is obtained sin (Zd) sin (L)|cos (Zd) cot(Br)=cot (Br) cos (L) solving for (Br), results in Y (5) cos (Zd) cot,(Br) =cot (Br) cos (L)-sin (Zd) sin (L) cot (Br) cos (L)sn (Zd) sin (L)cot (Br): cos (Zd) cot (Br) cos (L)sin (Zd) sin (L) (6) Br-cot 1|: Gos(Zd) Expression 6, the explicit solution for (Br) includes a cotangentfunction of quantity (Br). Since the cotangent function varies throughinnity for unlimited angle motion, Expression 6 is not satisfactory formechanization in a computer. By manipulating Expression 5 to containonly sine or cosine functions, a mathematical solution for this problemwill result which will be possible of mechanization. For that purpose,there is substituted into Expression 5 (ai) g g for coi (Br) (b1) Sgforcot (Br) resulting in cos (Zd) cos (Br) cos (Br) cos (L) sin (Br) sin(Bw) sin (Zd) sln (L) Clearing of fractions results in (7) cos (Zd) cos(Br) sin (Br) :cos (L) cos (Br) sin (Br) sin (L) sin (Zd) sin (Br) sin(Br) But:

as (B.) ,in (Ranma 3a-Bagan @+En Substituting a2, b and c2 in Expression7 15 (8) But sin (Br-Br)=sin (Br-B'r) cos (Zd) [-sin (Br-BW) +sin(Br-B'r)] =cos (L) [sin (Br-B'r) +sin (Br-|Br)] -sin (L) sin (Zd) [cos(Br-B'r) -cos (Br+B'r)] Multiplying out by coeicients -cos (Zd) sin(Br--Br) +cos (Zd) sin (Br-l-B'r) =cos (L) sin (Br-Br) +cos (L) sin(Br+B'r) sin (L) sin (Zd) [cos (Br-Br) -cos (Br+B'r)] Transposing liketerms and multiplying by minus one cos (zd) sin (Br-B'f)+os (L) sin(BrfB'f) =cos (Zd) sin (Br+B'r) -cos (L) sin (Br+Br) -l-sin (L) sin (Zd)[cos (.Br-B'r) cos (Br-|-Br)] Combining coeicients of common terms [cos(Zd) +cos (L)] sin (Br-Br) [cos (Zd) -cos(L)] sin (Br-i-Br) +sin (L) sin(Zd) [cos (Br-B'r) -cos (Br+B'r)] Let (jB'r) :(Br) -(B"r) 0: [cos (Zd)-cos (L)] sin (Br+B'r) +sin (L) sin (Zd) [cos (jB'r)-cos (Br+B'r)] [cos(Zd) +cos (L)] sin (jB'r) Therefore, the computation to be mechanizedinvolves the following three channels The computer for solving theEquation 10 is essentially one in which quantities' in the form of theproper functions of input and output quantities are added, subtractedand multiplied in each of three channels of computation. From Expression10, the summation of these three channels should be zero. Consequently,the output of a three input electrical differential or adding network isused as a servo input to drive in accordance with the deck tiltcorrection quantity. When the servo nulls the output of this network,the equation of this solution has been satisfied.

The specilic deck tilt corrector 14 employed for the mechanization ofthe Equation 10 is made up of a series of components, which may be ofany suitable design, and which per se, form no part of the presentinvention. Fig. 4 shows this deck tilt corrector 14 diagrammatically inblock form, and Fig. 5 shows as a specific example, an electricalschematic circuit diagram of the deck tilt corrector, the differentcomponent networks being shown schematically in their basic forms, thesolid lines in this latter diagram indicating electrical connections,and the dotted lines indicating mechanical lines or movements arising,for example, from shafts and rotations thereof.

The specific example of a deck tilt corrector shown in Fig. 5, utilizes400 cycle A.C. as a computing reference, with an input level of 12volts, the representation of data by the 400-cycle voltage being such,that the root mean square value of each voltage is proportional to thequantity represented. For the purpose of discussion, this referencevoltage is regarded as (+1). The different computed quantities areindicated in Figs. 4 and 5, without parametric coecients. Thesecoeicients are a function of the reference voltage (12 volts) and thecharacteristics of the constituent elements of the networks or loopsinvolved and are constant for any one mechanism. VFor example, in aresolver network of the potentiometer type having dual channelamplilier, such as that disclosed in copending application Serial No.33,186, tiled June 15, 1948, and operating with an input referencevoltage of 12 volts and with the mechanical input cross-level angle(Zd), the outputs will be -8 cos Zd and +8 cos Zd. The parametriccoeflicients -8 and +8 will however not be shown in Fig. 5 nor otherwiseindicated,

CHANNEL 1 [cos (Zd) +cos (L)] sin (jB'r) Referring to Figs. 4 and 5, themechanical cross-level quantity (Zd) from the stable element of theship, is brought as an input into a cosine computer 30, which may be ofany well-known suitable type, but which is shown in Fig. 5 as an anglefunction computer or resolver of the limited angle potentiometer type,disclosed in copending application Serial No. 33,186, led June 15, 1948.The input voltage reference (+1) and the mechanical quantity (Zd) arebrought into the potentiometer P30 of the computer 30 to obtain theoutputs +cos (Zd) and -cos (Zd).

The mechanical level quantity (L) from the stable element of the ship isbrought as an input into a suitable cosine computer 31, which may be ofany suitable type, but which is shown in Fig. 5 of the limited anglepotentiometer type disclosed in the aforesaid copending application.

The input voltage reference (+1) and the mechanical quantity (L) arebrought into the potentiometer P31 of the computer 31 to obtain theoutput -cos (L).-

The quantities -cos (Zd) and -cos (L) obtained from the resolvers 30 and31 respectively as described, are added in a suitable summing device3'2, indicated in Fig. 5 as an adding network, comprising two inputresistances in parallel, a computing amplifier (not shown) at the commonconnection of these resistors, having a very large gain, so as to drawno significant current from this point and maintain this connection at azero potential, a feedback resistor (not shown) and a load resistor (notshown). The different resistance ratios are selected to convert the twoinput voltages to a common scale, i.e. to the same value per volt.

The output of the summing device 32, namely cos (Zd) -i-cos (L) isbrought as an input to a sine computer 33, which may be of any suitabletype, but which is shown in Fig. of the magnetic type disclosed incopending application Serial No. 157,892, filed April 25, 1950, nowPatent No. 2,646,218. This electrical computer 33 comprises a computingresolver R33 and an error compensating resolver R'33, as described inthe latter application. The quantity (jB'r) is introduced into thecomputing resolver R33 through its rotor as previously described, andthe angle function computer 33 is so connected, that its operator is|sin (jB'r). The output of the angle function computer 33 is -[cos (Zd)-l-cos (L)] sin (J'B'r) which was previously specified as channel 1.

CHANNEL 2 +[cos (Zd)-cos (L)] sin (Br-I-B'r) The quantities +cos (Zd)and -cos (L) obtained from the computers 30 and 31 respectively asdescribed in connection with channel l, are added in a suitable summingdevice 34, indicated in Fig. 5 as an adding network of the parallelresistance type similar to the adding network 32. The resulting outputquantity is brought as an input to a suitable sine computer 35 having asmechanical inputs the quantities (2B'r) and (jB'r). This angle functioncomputer 35 is indicated in Fig. 5 as being of the magnetic type,similar to the computer 33 and similarly comprises a computing resolverR35 and an error compensating resolver R35.

The quantity (2Br) is the relative target bearing obtained from the gundirector or other source, multiplied by two through suitable gearing.This quantity (2B'r) drives the rotor of the computing resolver R35. Thedeck tilt correction (jBr) obtained from the output of the corrector 14drives the stator of the computing resolver R35 in a direction, so thatthe angle being operated upon is 2B'r-I-jBr which by the Expression 9becomes (Br-l-Br). The computing resolver R35 provides a (-}sin)operator, so that its output becomes -l-[cos (Zd)-cos (L)] sin (Br-i-Br)This expression conforms with channel 2.

The mechanical tilt correction (jB'r) derived from the output of thedeck tilt corrector is brought in as an input into a suitable cosinecomputer 36, indicated in Fig. 5 as a limited angle function computer ofthe potentiometer type, similar to the computer 30. The voltagereference (+1) and the mechanical quantity (jBr) are brought into thepotentiometer P36 of the computer 36 to obtain the output -l-cos (jB'r).

The mechanical quantity (Br--Br) obtained from the quantities (2Br) and(jBr) in the manner described in connection with the computer 35 isapplied as an input to a suitable cosine computer 37, indicated in Fig.5 as an angle function computer of the magnetic type, similar to thecomputer 33. The electrical reference (+1) and the mechanical quantity(Br-i-B'r) obtained as described are applied to the electrical computer37 of Fig. 5, the components of this mechanical quantity being fed tothe rotor and stator of the computing resolver part R37 of saidcomputer. The computer 37 provides a cos) operator, so that its outputbecomes -cos (Br-l-Br).

The quantities +cos (jBr) and -cos (Br-l-B'r) derived from the computers36 and 37 respectively as explained, are added in a suitable summingdevice 38, indicated in Fig. 5 of the parallel resistance network type,

8 similar to the adding network 32. The output of this summing device 38cos (jB'r)-cos (Br-{B'r) becomes the electrical input of a suitable sinecomputer 40, shown specifically in Fig. 5 of the limited anglepotentiometer type, disclosed in the aforesaid copending applicationSerial No. 33,186. This computer 40 has two potentiometers P40 and P40to serve as sine resolver. Into these potentiometers P40 and P'40 arefed the mechanical quantity (L) constituting the level angle obtainedfrom the stable element of the ship, to produce the output [cos(jBr)-cos (Br-i-B'l sin (L) The latter product of the sine computer 40becomesl an input of another sine computer 41, which may, for example,be a limited angle resolver of the potentiometer type, similar to theresolver 40, as shown in Fig. 5, having potentiometers P41 and P'41 withmechanical inputs (Zd) obtained from the stable element of the ship. Theoutput of this sine computer 41 will be -i-[cos (jBr)-cos (Br{-Br)] sin(L) sin (Zd) constituting the channel 3 referred to.

Production of (jB'r) from channels The three computation channel outputs[cos (Zd)+cos (L)] sin (jB'r) (channel 1) -l-[cos (Zd)-cos (L)] sin(Br-l-B'r) (channel 2) +sin (L) sin (Zd) [cos (jBr)-cos (Br}B'r)](channel 3) are conducted to a suitable summing device 42, shownspecifically in Fig. 5 of the parallel resistance type, similar to thesumming device 32, except that three input resistances are providedinstead of two. Theoretically, according to Equation l0, the summationof these computation channels should be zero. If the conditions of theEquation l0 are not satisfied, an error is produced at the output of thesumming device 42, which in the case of an electrical system such asthat of Fig. 5 is a voltage having the proper polarity to drive theservo motor of a servomechanism 43 of the well-known type, to produce anull in the error voltage. When this null is achieved, the value of(jBr) converted into a mechanical quantity (shaft rotation) becomes thedeck tilt correction desired. This quantity (J'B'r) when added to thcdirector train (Br) becomes the relative target bearing (Br).

A servomechanism, such as the servomechanism 43 is an automatic drivewhich positions a mechanical load in accurate correspondence with aninput, without placing an appreciable load upon this input. The inputcan be either mechanical or electrical (in Fig. 5, the input iselectrical) but the output is always mechanical.

The basic components of the specific servomechanism shown in Fig. 5comprises a servo control 45, a servo amplifier 46, a servo motor 47 andan induction generator 48 connected in a double loop circuit with acontrol network which in the present case is the summing loop 42.Essentially, the control network 42 computes a voitage proportional tothe error between a function of the input and a function of the output.This error voltage is converted to a frequency of 60 cycles by the servocontrol 45, amplified by the servo amplifier 46 and finally supplied tothe servo motor 47 for its control. 'Hte servo motor furnishes themechanical output and drives the induction generator 48. From thisgenerator 48, a voltage proportional to the output velocity is suppliedto the servo control 42. After being modified by computing elements inthe servo control 42, the modified voltage is combined with the errorvoltage to improve the operation of the servomechanism.

Equation 10 mechanized by the deck tilt correction 14 of the presentinvention can be expressed in different form, as for example, by thesubstitution of trigonometric 9 equivalents, without altering the basicsubstance of the equation. It should be understood therefore, that thereference to the specific equation in the following claim covers suchequivalent substitutions.

While the invention has been described with particular reference to aspecic embodiment, it is to be understood that it is not to be limitedthereto, but is to be construed broadly and restricted solely by thescope of the appended claim as interpreted in accordance with the aboveeX- planation.

What is claimed is:

A deck tilt corrector adaptable for a gun re control system forobtaining the quantity (jBr) representing decl: tilt correction,comprising means responsive to the quantity (jBr) as input obtained fromlthe output of the corrector for obtaining cos (jBr), means responsiveto the input (Zd) representing cross-level angle for obtaining -cos (Zd)and +cos (Zd), means responsive to the input (L) representing lev'elangle for obtaining -cos (L), means responsive to (jBr) and (Br)representing director train as inputs for obtaining (Br-l-B'r), in which(Br) represents relative target bearing, means responsive to (Br-i-B'r)as input for obtaining -cos (Br-i-B'r), means responsive to +cos (Zd)and -cos (L) as inputs for adding -l-cos (Zd) and -cos (L) to obtain cos(Zan-cos (L), means resopnsive to cos (Zd) -cos (L) 10 and (Br-l-Br) asinputs for obtaining the rst computation quantity [cos (Zd)-cos (L)] sin(Br-l-Br) means responsive to -cos (Zd) and -cos (L) as inputs foradding cos (Zd) and v-cos (L) for obtaining -[cos (Zd)|cos (L)], meansresponsive to -[cos (ZdH-cos (L)] and (jBr) as inputs, for obtaining thethird computation quantity -icos (Zd)'+cos (L)] sin (jBr) and a nullseeking device for equating the sum of said three computation quantitiesto zero and for obtaining thereby the quantity (jBr).

References Cited in the le of this patent UNITED STATES PATENTS2,658,675 Darlington Nov. 10, 19'53

